The two-volume set LNCS 15751 + 15752 constitutes revised selected papers from the 29th International Conference on Financial Cryptography and Data Security, FC 2025, which took place in Miyakojima, Japan, during April 14-18, 2025. The 42 full papers, 3 short papers and 1 Systematization of Knowledge paper included in the proceedings were carefully reviewed and selected from 300 submissions. They were organized in topical sections as follows: Part I; Layer 2; DeFi; zero-knowledge and its applications; modeling Bitcoin and incentives; efficient blockchains; broadcast; encryption and its applications; Part II: MEV; consensus; proof-of-X and rewards; signatures and threshold cryptography; machine learning.